Just a ping to have your valuable inputs here.
On 4/28/2023 8:32 PM, Charan Teja Kalla wrote:
> This patch aims to implement POSIX_FADV_WILLNEED and POSIX_FADV_DONTNEED
> advices to shmem files which can be helpful for the drivers who may want
> to manage the pages of shmem files on their own, like, that are created
> through shmem_file_setup[_with_mnt]().
>
> This patchset is unit tested with the below:
> (a) Qemu x86_64 with 4 smp cores, 2GB ram, 1Gb swap mounted
> on zram block device.
> (b) A tmpfs file of size 100MB is created.
> (c) Initially this file is filled with a poison value of 0xAA.
> (d) POSIX_FADV_[WILL|DONT]NEED is called on this file for a range that
> gets generated randomn. This is called for 10K iterations.
> (e) Check the poison value at the end of the test. Exit the program if it
> is changed.
>
> use the below script:
> val1=$(cat /proc/vmstat | grep pswpout | awk '{print $2}')
> str=$(./a.out <tmpfs file>)
> res=$(echo $str | awk '{print $1}')
> val2=$(cat /proc/vmstat | grep pswpout | awk '{print $2}')
>
> if [[ $res == "FAIL" ]]; then echo $str;
> else
> if [[ $val1 == $val2 ]]; then echo "FAIL. Does the swap setup is done?";
> else echo $res;
> fi
> fi
> ------------------------------------------------------------------------
> #include <stdio.h>
> #include <fcntl.h>
> #include <unistd.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/mman.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <sys/stat.h>
>
> #define NR_ITER (10000)
> unsigned int fd;
>
> void run_tests(int fd, loff_t start, loff_t end)
> {
>
> if (posix_fadvise(fd, start, end, POSIX_FADV_DONTNEED)) {
> perror("FAIL : fadvise():dont_need_thread\n");
> exit(6);
> }
>
> if (posix_fadvise(fd, start, end, POSIX_FADV_WILLNEED)) {
> perror("FAIL : fadvise():will_need_thread\n");
> exit(6);
> }
> }
>
> void get_rand_range(long size, loff_t *start, loff_t *end)
> {
> *start = rand() % (size >> 1);
> *end = *start + (rand() % size);
>
> if (*end > size)
> *start = *end = 0;
> }
>
> void fill_pattern(int fd, long size)
> {
> char *data;
>
> data = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
> if (data == MAP_FAILED) {
> perror("FAIL : mmap()\n");
> exit(5);
> }
> memset(data, 0xAA, size);
> munmap(data, size);
> }
>
> int check_pattern(int fd, long size)
> {
> unsigned char *data;
> long i;
>
> data = mmap(0, size, PROT_READ, MAP_SHARED, fd, 0);
> if (data == MAP_FAILED) {
> perror("FAIL : mmap()\n");
> exit(4);
> }
>
> for (i = 0; i < size; ++i) {
> if (data[i] != 0xAA) {
> printf("FAIL : Testcase is failed. Seeing %x rather than 0xAA\n", data[i]);
> exit(4);
> }
> }
> munmap(data, size);
> }
>
> int main(int argc, char **argv)
> {
> struct stat buf = {0};
> loff_t start, end, i;
>
> if (argc < 2) {
> printf("FAIL : usage: a.out <tmpfs filename>\n");
> exit(1);
> }
>
>
> if (stat(argv[1], &buf)) {
> perror("FAIL : stat()\n");
> exit(2);
> }
>
> fd = open(argv[1], O_RDWR);
> if (fd < 0) {
> perror("FAIL : open()\n");
> exit(3);
> }
>
> fill_pattern(fd, buf.st_size);
> for (i = NR_ITER; i > 0; --i) {
> get_rand_range(buf.st_size, &start, &end);
> run_tests(fd, start, end);
> }
> check_pattern(fd, buf.st_size);
>
> close(fd);
>
> printf("PASS \n");
>
> return 0;
> }
> ------------------------------------------------------------------------
>
> Changes in V8:
> -- Addressed the comments and fixed the bug caught by Hugh.
> -- Updated the commit message for POSIX_FADV_WILLNEED asked by Minchan.
>
> Changes in V7:
> -- Use folio based interface, shmem_read_folio(), for FADV_WILLNEED.
> -- Don't swap the SHM_LOCK'ed pages.
> -- https://lore.kernel.org/all/cover.1676378702.git.quic_charante@xxxxxxxxxxx/
>
> Changes in V6:
> -- Replaced the pages with folio's for shmem changes.
> -- https://lore.kernel.org/all/cover.1675690847.git.quic_charante@xxxxxxxxxxx/
>
> Changes in V5:
> -- Moved the 'endbyte' calculations to a header function for use by shmem_fadvise().
> -- Addressed comments from suren.
> -- No changes in resend. Retested on the latest tip.
> -- https://lore.kernel.org/all/cover.1648706231.git.quic_charante@xxxxxxxxxxx/
>
> Changes in V4:
> -- Changed the code to use reclaim_pages() to writeout the shmem pages to swap and then reclaim.
> -- Addressed comments from Mark Hemment and Matthew.
> -- fadvise() on shmem file may even unmap a page.
> -- https://patchwork.kernel.org/project/linux-mm/patch/1644572051-24091-1-git-send-email-quic_charante@xxxxxxxxxxx/
>
> Changes in V3:
> -- Considered THP pages while doing FADVISE_[DONT|WILL]NEED, identified by Matthew.
> -- xarray used properly, as identified by Matthew.
> -- Excluded mapped pages as it requires unmapping and the man pages of fadvise don't talk about them.
> -- RESEND: Fixed the compilation issue when CONFIG_TMPFS is not defined.
> -- https://patchwork.kernel.org/project/linux-mm/patch/1641488717-13865-1-git-send-email-quic_charante@xxxxxxxxxxx/
>
> Changes in V2:
> -- Rearranged the code to not to sleep with rcu_lock while using xas_() functionality.
> -- Addressed the comments from Suren.
> -- https://patchwork.kernel.org/project/linux-mm/patch/1638442253-1591-1-git-send-email-quic_charante@xxxxxxxxxxx/
>
> changes in V1:
> -- Created the interface for fadvise(2) to work on shmem files.
> -- https://patchwork.kernel.org/project/linux-mm/patch/1633701982-22302-1-git-send-email-charante@xxxxxxxxxxxxxx/
>
>
> Charan Teja Kalla (2):
> mm: fadvise: move 'endbyte' calculations to helper function
> mm: shmem: implement POSIX_FADV_[WILL|DONT]NEED for shmem
>
> mm/fadvise.c | 11 +----
> mm/internal.h | 21 ++++++++++
> mm/shmem.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 149 insertions(+), 10 deletions(-)
>
